1. Field of the Invention
The present invention relates to a dielectric device such as a dielectric resonator or a dielectric filter/duplexer composed thereof.
2. Description of the Related Art
Dielectric devices are used in a high-frequency range such as sub-microwave band, microwave band, millimeter wave band, or sub-millimeter wave band. More specific examples of applications include satellite communication devices, mobile communication devices, wireless communication devices, high-frequency communication devices, or base stations for such communication devices. The dielectric devices of this type are required to be miniaturized.
Japanese Patent No. 3329450 discloses a dielectric device whose resonator unit is composed of first and second holes provided in a dielectric substrate. The first hole opens on a first surface of the dielectric substrate and extends toward a second surface that is opposite to the first surface. The second hole has one end opening on a third surface that is not opposite to the first surface. The other end of the second hole is connected to the first hole in a T-junction form.
In such a T-junction hole configuration, the physical length corresponding to λ/2 or λ/4 is a sum of the length of the first hole and the length of the second hole. Therefore, unlike in the case of providing a single straight hole in the dielectric substrate, the desired physical length can be obtained by adjusting the length of one hole to compensate for the length of the other hole. Thus, the length of the dielectric substrate can be shortened to achieve miniaturization.
As described above, the T-junction hole configuration enables shortening the length of the dielectric substrate to achieve miniaturization, but further miniaturization is expected. For further miniaturization, it is also expected to modify the T-junction hole configuration to lower resonant frequency without sacrificing easiness of production.